Sir Peter Fahy says there is an ­embarrassing paucity of black and minority ­ethnic ­officers at the top of British policing. Photograph: Dave Thompson/PA

Police forces should be made to positively discriminate in favour of black and ethnic minority officers in the face of a growing diversity crisis, according to one of the country's leading chief constables.

The radical proposal – which would mean a change in the law – from Sir Peter Fahy, of Greater Manchester, comes in the face of what he said was an embarrassing paucity of black and minority ethnic officers (BME) at the top of British policing.

Fahy, the lead spokesperson on workforce development for the Association of Chief Police Officers (Acpo), spoke as Theresa May, the home secretary, was due to announce plans this week to introduce direct entry to the service at inspector and superintendent ranks as part of the Winsor reforms.

Some chief officers believe this will help improve diversity, but Fahy said the small numbers involved would not significantly change the white face of British policing.

This year the lack of BME senior officers rising through the ranks of the service is starkly illustrated by the fact that there are none on the strategic command course – for middle-ranking officers seeking promotion to chief officer rank.

Fahy said the budget cuts and reduction in middle management within the service meant the diversity problem was only going to get worse. He wants the creation of a more diverse police service to be a legal requirement.

"This is not about targets or political correctness," he said. "It is about operational need. Policing is unique, we need to be legitimate within the community because of the exercise of power. Often we are out there resolving disputes between communities and we need officers that understand different communities and different backgrounds.

"Then there is the practical stuff about surveillance and undercover officers. We need to be a more diverse police service. The operational need is great."

Credit: Guardian graphics

There are 48 BME superintendents and chief superintendents in England and Wales, and six chief officers – representing 3% of all chiefs.

Damian Green, the police minister, told police and crime commissioners last week that he was "struck by how far we still need to improve representation of women, black/minority ethnic populations and other protected groups in the police, especially at senior levels".

But he made clear that it was up to the police, not the government, to take responsibility for improving the situation. "My firm belief is that the police must take ownership for these issues."

Fahy said there was a lack of political will to drive change and make the police service more ethnically diverse.

He was supported by Sir Hugh Orde, president of Acpo, who called for an urgent debate on changing the law, citing the reforms in Northern Ireland after the Patten report making it a legal requirement that if a protestant officer were to be recruited a Catholic had to be taken on as well.

"There is a real issue in senior ranks that we are not representative of the population we are policing," said Orde.

"There should be a real, constructive conversation about how we move forward because this is something that has been difficult for years."

Sir Bernard Hogan-Howe, commissioner of the Metropolitan police, also indicated he would support a law change but said other measures, such as direct entry, should be tried first to help increase diversity before legal steps were taken.

Fahy said while better progress was being made with women rising through the ranks – four females were appointed to chief constable posts last week – the same was not true of BME officers.

"It is really disappointing and frustrating and I am embarrassed by the lack of progress."

He predicted the situation would get worse as the cutbacks took hold, removing senior posts from the service, reducing the opportunity for promotion and increasing competition for senior roles.

"It is going to be more difficult to increase diversity now. We are reducing the number of senior ranks – we draw chief constables from chief superintendent rank, and that is being reduced by 40%.

"What you will get is a big reaction in the organisation with people being very competitive and there's an internal reaction against people being seen to get on in an organisation because of their ethnic background."

The 48 BME superintendents and chief superintendents across the country, he said, would be under huge pressure to rise through the ranks and to be role models and standard bearers as they did so.

"We are trying to support them, but you have to be realistic. You have to be a chief superintendent two to three years before you can be a chief officer.

"We can't put people through who are going to be see to fail."

Police chief officers are waiting to see the details of May's proposals this week. Tom Winsor recommends an intake of 40 inspectors from outside the police service each year and 20 superintendents.

Charles Crichlow, president of the National Black Police Association, said senior officers such as Fahy had it within their power to force more change and direct entry was one way to do it.

"No one takes responsibility for this. Sir Peter Fahy blames the politicians for not taking this on, the politicians blame the police and meanwhile nothing is done," he said.

"I am not suggesting direct entry is a silver bullet.

"But if they were really concerned about ethnic diversity then they could and should say for the first tranche of recruits for direct entry we are going to focus specifically on ethnic diversity. It is in their power to do that."

Success stories

Pat Gallan Assistant commissioner, Metropolitan police Britain's highest-ranking black policewoman. Joined the Met police as a constable in 1987 and served in the East End before joining CID. In 2012 she returned to Scotland Yard from Merseyside where she was temporary deputy chief constable. She is a qualified barrister.

Chief Superintendent Dal Babu Metropolitan police officer, Harrow One of Britain's most senior Muslim officers, he is chairman of the Association of Muslim Officers. Joined the Met police in 1983. Has a master of science from London university.

Mak Chishty Commander for Metropolitan police, Holborn Born in Birmingham, and joined the police at 18. Spent many years in CID before becoming borough commander in Rugby, with Warwickshire police. Moved to the Met in 2011, as commander for north London. Has a law degree.

Max Sohata Temporary deputy chief constable, South Yorkshire police Joined Warwickshire police as a university graduate. Promoted from chief superintendent at West Midlands police, to assistant chief constable for South Yorkshire in 2008.